1. Field of the Invention
The present invention relates to a method of cleaning a substrate surface employed prior to film formation by using the CVD (Chemical Vapor Deposition) method which uses a reaction gas (hereinafter referred to as an "O.sub.3 /TEOS reaction gas") containing an ozone containing gas which contains ozone (O.sub.3) in oxygen (O.sub.2) and tetraethylorthosilicate (TEOS), and a method of manufacturing a semiconductor device using the above method.
2. Description of the Prior Art
In recent years, an insulating film can be formed by the CVD method using the O.sub.3 /TEOS reaction gas (hereinafter referred to as an "O.sub.3 /TEOS-CVDSiO.sub.2 film"). The insulating film has fine quality and a smaller etching rate, is not shrunk in the high temperature heating process, has less moisture content, and has better flow performance as the O.sub.3 concentration in O.sub.2 becomes higher. Where a silicon oxide film which is formed by using the O.sub.3 /TEOS reaction gas containing the high concentration O.sub.3 (called a "High O.sub.3 /TEOS reaction gas" hereinafter) is called a High O.sub.3 /TEOS-CVDSiO.sub.2 film, and the O.sub.3 /TEOS reaction gas containing the low concentration O.sub.3 is called a "Low O.sub.3 /TEOS reaction gas.
Meanwhile, in the case that the High O.sub.3 /TEOS reaction gas is employed, a degree of influence of the film formation upon surface conditions of a film-forming surface (referred to as "surface dependency" hereinafter) is increased. Where the film forming surface corresponds to a surface of a substrate on which a film is planed to be formed. More particularly, it has been known that, if as shown in FIG. 1A, a particular extraneous substance, i.e., an particle 3 are present on a film-forming surface 2 of a substrate 1, such particle 3 is melted down at the film forming temperature to spread over (such area is indicated by a reference 3b), as shown in FIG. 1B, and then a deposition rate of the High O.sub.3 /TEOS-CVDSiO.sub.2 film 4 is extremely lowered in a range of several tens .mu.m to several mm in diameter around the almost circular area, otherwise the High O.sub.3 /TEOS-CVDSiO.sub.2 film 4 is not deposited at all in the same range, as shown in FIG. 1C. This abnormal film forming phenomenon is often called a circular defect, a spot fault, or the like.
In the prior art, prior to the formation of the O.sub.3 /TEOS-CVDSiO.sub.2 film, these extraneous particles are removed by cleaning the substrate by the wet cleaning in the pure water. FIG. 2 is a flowchart showing the film forming steps containing the pre-processing step according to the prior art.
The circumstances in the clean room which is prepared to manufacture the semiconductor device can be kept clean since floating particles are small in number. Nevertheless, since the particles are produced due to the human being such as the operator in many cases, such particles are often detected from an inside of the clean room. Accordingly, even if the substrate 1 is cleaned previously by the wet cleaning, there is a high possibility that such particles are stuck to the substrate 1 again in the clean room. As a result, it has been difficult to remove the foregoing circular defect in the prior art.